Selenium rectifier and photocell



Oct. 25, 1949. F, GRAY 2,485,589v

SELENIUM RECTIFIER AND PHoTocELL Filed lay 9, 1946 ATTORNEY Patented Oct. 25, 1949 SELENIUM micrrrmn AND rno'rocnu.

Frank Gray, London, England, assignor, by mesne assignments, to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application May 9, 1946, Serial No. 668,361 In Great Britain November 2, 1944 Section 1, Public Law .690, August 8, 1946 Patent expires November 2f, 1964 This invention relates to selenium cells such as electrical dry rectiilers or photo-cells and the term selenium cells as used herein embraces both of these types of apparatus.

One of the most prevalent cau-ses of rejection during the manufacture of such rectiflers or cells is the existence of short circuits between the base plate and the counter electrode due to uneven spreading of the intervening layer of selenium, and to impurities in the selenium.

The best cure is, of course, to ensure a selenium layer of uniform thickness and free from impurities on all plates manufactured.

At present this is a counsel of perfection hard to live up to, and the object of the present invention is to provide a palliative which will largely prevent short circuits occurring even when the conditions which normally produce them are present.

According to the invention, a very small percentage of a thermo-setting resin, such as a v phenol formaldehyde is mixed with the selenium before it is applied to the base-plate. The proportion is not critical, but 13% gives the best' results. v

The invention will be clearly understood from the following description taken in conJunction with the accompanying drawing which shows diagrammatically the action of the resin in pre.

venting short circuits.

In the drawing, I is the base plate of nickelplated mild steel, with roughened surface on which a layer of selenium 2 is formed in intimate contact therewith.

A counter-electrode layer l of a known alloy is prayezd or otherwise deposited on the selenium ayer The selenium before being deposited on the base plate I in powder form is mixed with 13% of a thermo-setting resin such as phenol formaldehyde.

It has been found that if there is a thin spot in the selenium layer the resin tends to concentrate at the spot and form an insulating layer 4 Claims. (Cl. 175-366) 2 as indicated by the reference character I in the drawing between the two electrode surfaces thus preventing a short circuit at the spot. but, so

long as only a very small proportion of the surface is so insulated, having no deleterious effect on the performance of the rectiers.

The remainder of the resin will be distributed in grains throughout the selenium as indicated.

It will be seen therefore that the admixture of a little resin powder with the selenium acts to minimise the lrejections due to short-circuits.

What is claimed is:

l. In a selenium cell of the type wherein a layer of selenium is provided upon a metallic base element, the improvement that comprises including in the selenium layer a powdered thermosetting synthetic resin distributed throughout the selenium layer.

. 2. A selenium cell as dened in claim 1 wherein the thermo-setting synthetic resin is of the phenol-formaldehyde type.

3. A selenium cell as defined in claim 1 wherein the thermo-setting synthetic resin is present in an amount of one to three weight percent, based on the selenium.

4. Aselenium cell as defined in claim 1 wherein the thermo-setting synthetic resin is of the phenol-formaldehyde type and is present in an amount of one to three weight percent, based on the selenium.

. FRANK GRAY.

REFERENCES CITED 'I'he following references are of record in the 

